fix duplicate models that sneaked in while rebasing.
fix duplicate models that sneaked in while rebasing.

pombredanne/django-simple-history,luzfcb/django-simple-history,pombredanne/django-simple-history,treyhunner/django-simple-history,luzfcb/django-simple-history,emergence/django-simple-history,treyhunner/django-simple-history,emergence/django-simple-history